JPH1110821A - Manufacture of light-weight fiber-reinforced resin composite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a light-weight fiber-reinforced composite wherein the expansion ratio of the foaming layer can be freely selected, by using inexpensive materials. SOLUTION: A sheet molding compound is superposed on at least one surface of a foaming resin sheet containing a decomposable foaming agent to form a laminated body, and the laminated body is guided to a heat-compressing device, and first, the laminated body is heated to a decomposition temperature of the foaming agent in the decomposable resin sheet, and the foaming agent is decomposed. Then, the laminated body is heated to a hardening temperature of the sheet molding compound, and the foaming of the sheet and the hardening of the sheet molding compound are performed. Then, the expanded sheet and the sheet molding compound under hardening are bonded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a fiber-reinforced resin composite.

[0002]

2. Description of the Related Art Heretofore, as a fiber-reinforced resin composite used for a wall material for a house, a ceiling material of an automobile, and the like, a sheet molding compound (hereinafter abbreviated as SMC) formed by heating and pressing is well known. . In recent years, heat insulation, sound absorption, light weight, etc. have been required for the above-mentioned applications and the like. For this purpose, a method of laminating a foam sheet to a heated and pressurized molded article of SMC by post-processing has been carried out. Have been done. Further, Japanese Patent Application Laid-Open No. Hei 8-230085 proposes a method of laminating an uncured SMC and a foam sheet or a honeycomb sheet and heating and pressurizing to obtain a lightweight and heat-insulating molded article. .

However, all of the above-mentioned prior arts are batch-type manufacturing methods, and thus have a problem of low productivity.

As a method for solving this problem, Japanese Patent Laid-Open No.
Japanese Patent No. 187738 discloses a method for continuously producing a fiber-reinforced resin composite in which a lightweight core material is formed using a resin composition containing rigid lightweight hollow particles, and the front and back surface layers are made of a fiber-reinforced resin. Has been proposed.

However, a lightweight resin body (so-called syntactic foam) mixed with rigid lightweight hollow particles has a problem that the rigid lightweight hollow particles used are expensive and it is difficult to arbitrarily change the specific gravity of the obtained lightweight resin body. is there.

[0006]

SUMMARY OF THE INVENTION The object of the present invention has been made in view of the above-mentioned circumstances, and is made of a light-weight material that can use a low-cost material and can freely select the expansion ratio of a foam layer. An object of the present invention is to provide a method for producing a fiber-reinforced resin composite.

[0007]

According to the present invention, there is provided a method for producing a lightweight fiber-reinforced resin composite, comprising forming a laminate by laminating a sheet molding compound on at least one surface of a foamable resin sheet containing a decomposable foaming agent. The laminated body is guided to a heating and compression device, and first heated to the decomposition temperature of the foaming agent in the foamable resin sheet to decompose the foaming agent, and then heated to the curing temperature of the sheet molding compound to foam the sheet. And curing the sheet molding compound and joining the foamed sheet and the sheet molding compound being cured.

As the foamable resin sheet used in the present invention, a decomposable foaming agent is blended with a thermoplastic resin so as to have a desired expansion ratio, and if necessary, a crosslinking agent, a filler, a coloring agent, etc. are added. The sheet is formed by a conventionally known molding technique.

Examples of the thermoplastic resin include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polystyrene, polyvinyl chloride and the like.

The foaming agent is one which decomposes upon heating to generate a gas. For example, inorganic systems such as sodium bicarbonate and ammonium bicarbonate: such as azodicarbonamide and azobisisobutyronitrile Azo compounds: nitroso compounds such as dinitrosopentamethylenetetramine: paratoluenesulfonyl hydrazide,
and hydrazide compounds such as pp'oxybis (benzenesulfonyl hydrazide). If necessary, foaming aids such as urea and metal salts of carboxylic acids are also used.

The selection of the foaming agent is made in consideration of the softening temperature of the thermoplastic resin used, the curing temperature of the SMC used, and the like. The foaming agent used in the present invention is limited to those whose foaming temperature is lower than the curing temperature of the SMC used. The difference between the foaming temperature of the foaming agent and the curing temperature of the SMC is preferably up to 30 ° C. The above S
The curing temperature of MC refers to the temperature at which the gel time measured by a curastometer is 10 seconds.

[0012] The SMC used in the present invention includes a thermosetting resin, a reinforcing fiber, a filler, a low shrinkage material, a thickener, a curing agent, a mold release, which are manufactured by a conventionally known SMC manufacturing apparatus and manufacturing process. Of general composition consisting of agents and other compounding agents
MC is used.

The thermosetting resin includes, for example, unsaturated polyester resin, vinyl ester resin, phenol resin, epoxy resin and the like. Unsaturated polyester resins are preferred in terms of price, performance, and the like.

As the SMC composition used in the present invention, those which can be molded by low pressure heating and pressing can also be used.
As an example thereof, there is a composition as proposed in JP-A-8-41307.

[0015] As the heating and compression device in the present invention, a continuous heating and compression device comprising a pair of upper and lower conveyor belts is usually used. The material of the belt is preferably made of fluororesin from the viewpoint of heat resistance. The upper and lower gaps of the pair of upper and lower conveyor belts are adjustable, and the temperature of the belts is also adjustable. The pair of upper and lower conveyor belts decompose the foaming agent in the foamable resin sheet (in some cases, foam the resin sheet),
It is preferable that the number is three in order to harden and cool the MC, but in some cases, the number may be more than three.

(Function) In the method for producing a lightweight fiber-reinforced resin composite of the present invention, an SMC is laminated on at least one surface of a foamable resin sheet containing a decomposable foaming agent to form a laminate.
The laminated body is guided to a heating and compression device, and first heated to the decomposition temperature of the foaming agent in the foamable resin sheet to decompose the foaming agent, and then heated to the curing temperature of the SMC to foam the sheet and form the SMC. It is a method of joining the foamed sheet and the SMC during curing, while performing the curing of
The expansion ratio of the foamable resin sheet can be freely changed, and the SMC is formed by the foaming pressure of the foamable resin sheet. Therefore, the process is simple, and the SMC is formed in the bubbles of the foamed resin layer. The resin that has entered penetrates to cause an anchoring effect, and the adhesion between the cured SMC layer and the foamed resin layer becomes strong.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below together with comparative examples. FIG. 1 is a simplified cross-sectional view of a continuous heating and compression apparatus used for manufacturing an example and a comparative example.

Example 1 Preparation of foamable resin sheet 100 parts by weight of low-density polyethylene, p-type as a foaming agent
p 'Oxybis (benzenesulfonyl hydrazide)
(Decomposition temperature: 130 to 140 ° C.) 10 parts by weight and 1 part by weight of dicumyl peroxide as a crosslinking agent were supplied to an extruder and kneaded and extruded to obtain a foamable resin sheet having a thickness of 2 mm, which was wound around a roll.

Preparation of SMC 40 parts by weight of unsaturated polyester resin, polystyrene 15
35 parts by weight of styrene monomer, 130 parts by weight of calcium carbonate (average particle size: 2 μm), 0.5 part by weight of ditertiary butyl peroxybenzoate as a curing agent, and 0.8 part by weight of magnesium oxide are kneaded into a paste. This was supplied to a conventionally known SMC manufacturing apparatus to form a 2 mm-thick composite having a glass fiber content of 20% by weight, and the composite was thickened at 40 ° C. for 24 hours to obtain an SMC.
And wound up on a roll. The curing temperature of this SMC is 1
It was at 50 ° C.

Production of Fiber Reinforced Resin Composite 11 in FIG. 1 is a roll for feeding a foamable resin sheet, from which a foamable resin sheet 14 is drawn. 2
Reference numerals 1 and 21 denote SMC feeding rolls provided on the upper and lower sides. The release films on the front and back sides are peeled off, and the SMC 24 is wound on the release film winding rolls 22 and 22;
24 was supplied to the gap between a pair of upper and lower conveyor belts 51 (hereinafter, referred to as belt 1) with the foamable resin sheet 14 interposed therebetween. At this time, the temperature of the belt 1 is 13
The upper and lower gap was 5 mm at 5 ° C.

While passing through the belt 1, the foaming agent in the foamable resin sheet 14 is decomposed and foaming force is built in. Immediately after passing through the belt 1, the foaming of the sheet 14 starts, and then the second upper and lower The belt 2 is guided to a pair of conveyor belts 52 (hereinafter, referred to as belt 2; the temperature of the belt 2 is 160 ° C., and the gap is 25 mm). Upper and lower SMC 24,
The sheet 24 was pressed against the conveyor belts 52, 52, and was formed into a plate shape and cured by the belt temperature.

The composite that has left the belt 2 is the third upper and lower 1
A pair of conveyor belts 53, 53 (hereinafter referred to as belt 3).
The temperature of the belt 3 is 10 ° C., and the gap is 20 mm. ), The belt 3 cools and shapes the belt, and the composite 34
I got The line speed of each of belts 1, 2, and 3 is 2m
/ Min.

Example 2 The thickness of the foamable resin sheet 14 was 4 mm, and the gaps between the belts 1, 2, and 3 were 8 mm, 48 mm, and 40 m, respectively.
Except having set it to m, it carried out similarly to Example 1, and obtained the composite body 34.

Embodiment 3 The above-mentioned SMC 24 is provided only at one of the upper portions, and the belts 1, 2,
A composite 34 was obtained in the same manner as in Example 1 except that the gaps of Nos. 3 were set to 4 mm, 22 mm, and 20 mm, respectively.

Comparative Example 1 The procedure of Example 1 was repeated except that the foaming agent used for the foamable resin sheet 14 was azodicarbonamide (decomposition temperature: 195 to 202 ° C.). At the belt temperature of Example 1, the foamable resin sheet 14 did not foam, and the desired lightweight composite was not obtained.

Comparative Example 2 The same procedure as in Example 1 was carried out except that the same foamable resin sheet 14 as used in Comparative Example 1 was used, and the temperatures of the belts 1 and 2 were both set to 200 ° C. In Comparative Example 2, the curing of the SMC started before the foaming of the foamable resin sheet 14, so that only a composite having insufficient bonding at the interface between the cured SMC and the foamed layer was obtained.

Comparative Example 3 The procedure of Example 1 was repeated except that the curing agent for SMC21 was changed to t-butyl hydroperoxide. The curing temperature of the SMC used in Comparative Example 3 was 180 ° C., and the SMC did not cure at each belt temperature in Example 1.

Evaluation The composites obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were cut,
The interface between the cured SMC layer and the foamed layer was observed to evaluate the adhesiveness. In the case of poor adhesion, peeling occurred at the interface during cutting, but this was evaluated as x, and in the case of no peeling, evaluated as ○. The results are shown in Table 1. In addition, the cross section was observed with a 20 × optical microscope, and the SMC into the bubbles of the foamed layer was observed.
The degree of penetration of the cured resin from the resin was evaluated, and the results are shown in Table 1 with the case where the resin penetrated into the bubbles as ○ and the case where the resin did not enter as ×.

[0029]

[Table 1]

[0030]

The structure of the method for producing a lightweight fiber-reinforced resin composite of the present invention is as described above.
The expansion ratio of the foamable resin sheet can be freely changed, and the SMC is formed by the foaming pressure of the foamable resin sheet. Therefore, the process is simple, and the SMC is formed in the bubbles of the foamed resin layer. As a result, an anchoring effect is caused by the infiltrated resin, and a light-weight fiber-reinforced composite having strong adhesion between the cured SMC layer and the foamed resin layer can be obtained.

[Brief description of the drawings]

FIG. 1 is a simplified cross-sectional view showing an example of a continuous heating and compression apparatus used for carrying out the present invention.

[Explanation of symbols]

 11, 21 Feeding roll 14 Foamable resin sheet 22 Take-up roll 24 SMC 34 Composite 51, 52, 53 Conveyor belt

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29K 105: 04 105: 08 B29L 31:10

Claims (1)

[Claims] 1. A foamed resin sheet containing a decomposable foaming agent, a sheet molding compound is superposed on at least one side of the foamed resin sheet to form a laminate, and the laminate is guided to a heating and compression apparatus. The foaming agent is decomposed by heating to the decomposition temperature of the foaming agent, and then heated to the curing temperature of the sheet molding compound to foam the sheet and cure the sheet molding compound, and to cure the foamed sheet and the A method for producing a lightweight fiber-reinforced resin composite, which comprises joining a sheet molding compound.